Field of the Invention
The present invention relates to an inkjet recording apparatus which records an image on a paper sheet conveyed through a fixed conveying path by an inkjet method.
Description of the Related Art
In the inkjet recording apparatus, paper sheets need to be conveyed in a flat state. When floating, such as wrinkles and folding, is present in a paper sheet, not only may image quality deteriorate, but also the paper sheet may contact inkjet heads, and the inkjet heads may be damaged in the worst case.
Accordingly, in conventional inkjet recording apparatuses, floating of the paper sheet is detected on the upstream side of an inkjet recording unit. When the detected floating is equal to or more than a fixed level, conveyance of the paper sheet is stopped to prevent the paper sheet from contacting the inkjet heads (see, for example, Japanese Patent Application Laid-Open No. 2010-076872). When conveyance of the paper sheet is stopped, an operator visually confirms a floating generation status and performs adjustment of a paper feeding system or a conveyance system in accordance with the type of the generated floating.
However, when conveyance of the paper sheet is stopped, it causes not only a problem that the paper sheet currently under recording is wasted, but also a problem that paper sheets under preprocessing and post-processing within the apparatus are wasted. Moreover, once the conveyance is stopped, restarting takes time so that productivity also deteriorates.
As a solution to such problems, there is known a technique of retreating the inkjet heads to prevent the paper sheet from contacting the inkjet heads when floating is generated in the paper sheet (see, for example, Japanese Patent Application Laid-Open No. 2012-143944). The solution presents an effect that can suppress generation of waste sheets to a minimum.
However, when conveyance of the paper sheet is continued, it becomes impossible to confirm the floating generation status, which causes a situation in which necessary adjustment cannot be performed.
To cope with this situation, techniques of reading the surface of a paper sheet with a scanner and analyzing the obtained image to detect wrinkles and the like generated in the paper sheet are disclosed in Japanese Patent Laid-Open No. 2007-301920, Japanese Patent Application Laid-Open No. 2006-084595, Japanese Patent Application Laid-Open No. 2015-037982, and Japanese Patent Application Laid-Open No. 2006-298606.